1. Field of the Invention
The present invention relates to a method of forming a main pole of a thermally-assisted magnetic recording head which performs data writing by irradiating a recording medium with near-field light to lower the coercivity of the recording medium, and a method of manufacturing the thermally-assisted magnetic recording head.
2. Description of the Related Art
Recently, magnetic recording devices such as magnetic disk drives have been improved in recording density, and thin-film magnetic heads and recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a read head including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head including an induction-type electromagnetic transducer for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the magnetic recording medium.
To increase the recording density of a magnetic recording device, it is effective to make the magnetic fine particles of the recording medium smaller. Making the magnetic fine particles smaller, however, causes the problem that the magnetic fine particles drop in the thermal stability of magnetization. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the recording medium, and this makes it difficult to perform data writing with existing magnetic heads.
To solve the foregoing problems, there has been proposed a technology so-called thermally-assisted magnetic recording. The technology uses a recording medium having high coercivity. When writing data, a write magnetic field and heat are simultaneously applied to the area of the recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization. Hereinafter, a magnetic head for use in thermally-assisted magnetic recording will be referred to as a thermally-assisted magnetic recording head.
In thermally-assisted magnetic recording, near-field light is typically used as a means for applying heat to the recording medium. A known method for generating near-field light is to use a plasmon generator, which is a piece of metal that generates near-field light from plasmons excited by irradiation with laser light. The laser light to be used for generating the near-field light is typically guided through a waveguide, which is provided in the slider, to the plasmon generator disposed near a medium facing surface of the slider.
U.S. Patent Application Publication No. 2010/0172220 A1 discloses a technology for coupling the light that propagates through the waveguide with the plasmon generator in surface plasmon mode via a buffer part, thereby exciting surface plasmons on the plasmon generator.
For a thermally-assisted magnetic recording head having the aforementioned waveguide and plasmon generator and a main pole for producing a write magnetic field, it is required that the main pole, a part of the core of the waveguide, and the plasmon generator be disposed in a very small region in the vicinity of the medium facing surface.
To meet the aforementioned requirement, the thermally-assisted magnetic recording head may be configured such that the core is located farther from the top surface of the substrate than is the plasmon generator, the core has an end face that faces toward the medium facing surface and that is located away from the medium facing surface, and the main pole is interposed between the medium facing surface and the end face of the core.
In the aforementioned configuration, the main pole has a front end face, i.e., an end face located in the medium facing surface, and a rear end face or the other end face that is opposite to the front end face. To employ the aforementioned configuration, it is required that a large write magnetic field be locally generated from a part of the front end face of the main pole located close to the plasmon generator. For that purpose, the front end face of the main pole preferably has such a shape that a first end closer to the top surface of the substrate is smaller in width in the track width direction than a second end farther from the top surface of the substrate.
To employ the aforementioned configuration, it is further required that the light propagating through the core be efficiently transformed into near-field light. To this end, it is preferred that the end face of the core facing toward the medium facing surface be as close to the medium facing surface as possible in order to allow the plasmon generator to excite surface plasmons at the nearest possible point to the medium facing surface. Furthermore, a larger contact area between the end face of the core and the rear end face of the main pole leads to a greater ratio of the amount of light absorbed by the main pole to the amount of light propagating through the core. It is therefore preferable to reduce the contact area between the end face of the core and the rear end face of the main pole as much as possible. Taking these into account, it is preferred that the rear end face of the main pole be perpendicular or almost perpendicular to the top surface of the substrate.
As can be seen from the discussions above, to employ the aforementioned configuration, the main pole preferably has such a shape that the rear end face is perpendicular or almost perpendicular to the top surface of the substrate, and the first end of the front end face is smaller in width in the track width direction than the second end of the front end face. However, it is not easy to form a main pole of such a shape.